1. Field of the Invention
The present invention relates to an inverter which supplies driving voltage to an external electrode fluorescent lamp.
2. Description of the Related Art
In recent years, liquid crystal display TVs, which provide a TV having a thin shape and a large size, are becoming popular as replacements for CRT-based TVs. Liquid crystal display TVs include multiple cold cathode fluorescent lamps (which will be referred to as “CCFLs” hereafter) or external electrode fluorescent lamps (which will be referred to as “EEFLS” hereafter) arranged on the back face of a liquid crystal panel on which video images are to be displayed, which are used as light-emitting backlights.
The CCFL or EEFL is driven using an inverter (DC/AC converter) which boosts DC voltage of around 12 V, and which outputs the voltage thus boosted in the form of AC voltage, for example. The inverter converts the current flowing through the CCFL into voltage, and returns the voltage thus converted to a control circuit as a feedback voltage, thereby controlling the ON/OFF operation of a switching element based upon this feedback voltage. For example, a CCFL driving technique using such an inverter is disclosed in Patent document 1.
[Patent Document 1]
Japanese Patent Application Laid Open No. 2003-323994
EEFLs have a problem in that it is difficult to turn on an EEFL as compared with other fluorescent lamps such as CCFLs. Whether or not the EEFL is switched to a light-emission state is a matter of probability. Accordingly, in order to ensure that the EEFL emits light, conventional inverters repeatedly perform a start-up operation several times, thereby raising the probability of light emission. Specifically, in order to perform EEFL striking, conventional inverters repeatedly perform an operation in which high voltage is applied to the inverter and the inverter is shut down.
Such conventional techniques require an external circuit which repeatedly performs the shut down operation and the start-up operation of a control circuit for the inverter, in addition to the control circuit. This leads to a large circuit area and high costs.